/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xml.internal.resolver.helpers;

/**
 * Static methods for dealing with public identifiers.
 *
 * <p>This class defines a set of static methods that can be called
 * to handle public identifiers.</p>
 *
 * @author Norman Walsh
 * <a href="mailto:Norman.Walsh@Sun.COM">Norman.Walsh@Sun.COM</a>
 */
public abstract class PublicId {

    protected PublicId() {
    }

    /**
     * Normalize a public identifier.
     *
     * <p>Public identifiers must be normalized according to the following
     * rules before comparisons between them can be made:</p>
     *
     * <ul>
     * <li>Whitespace characters are normalized to spaces (e.g., line feeds,
     * tabs, etc. become spaces).</li>
     * <li>Leading and trailing whitespace is removed.</li>
     * <li>Multiple internal whitespaces are normalized to a single
     * space.</li>
     * </ul>
     *
     * <p>This method is declared static so that other classes
     * can use it directly.</p>
     *
     * @param publicId The unnormalized public identifier.
     * @return The normalized identifier.
     */
    public static String normalize(String publicId) {
        String normal = publicId.replace('\t', ' ');
        normal = normal.replace('\r', ' ');
        normal = normal.replace('\n', ' ');
        normal = normal.trim();

        int pos;

        while ((pos = normal.indexOf("  ")) >= 0) {
            normal = normal.substring(0, pos) + normal.substring(pos + 1);
        }
        return normal;
    }

    /**
     * Encode a public identifier as a "publicid" URN.
     *
     * <p>This method is declared static so that other classes
     * can use it directly.</p>
     *
     * @param publicId The unnormalized public identifier.
     * @return The normalized identifier.
     */
    public static String encodeURN(String publicId) {
        String urn = PublicId.normalize(publicId);

        urn = PublicId.stringReplace(urn, "%", "%25");
        urn = PublicId.stringReplace(urn, ";", "%3B");
        urn = PublicId.stringReplace(urn, "'", "%27");
        urn = PublicId.stringReplace(urn, "?", "%3F");
        urn = PublicId.stringReplace(urn, "#", "%23");
        urn = PublicId.stringReplace(urn, "+", "%2B");
        urn = PublicId.stringReplace(urn, " ", "+");
        urn = PublicId.stringReplace(urn, "::", ";");
        urn = PublicId.stringReplace(urn, ":", "%3A");
        urn = PublicId.stringReplace(urn, "//", ":");
        urn = PublicId.stringReplace(urn, "/", "%2F");

        StringBuilder buffer = new StringBuilder(13 + urn.length());
        buffer.append("urn:publicid:");
        buffer.append(urn);
        return buffer.toString();
    }

    /**
     * Decode a "publicid" URN into a public identifier.
     *
     * <p>This method is declared static so that other classes
     * can use it directly.</p>
     *
     * @param urn The urn:publicid: URN
     * @return The normalized identifier.
     */
    public static String decodeURN(String urn) {
        String publicId;
        if (urn.startsWith("urn:publicid:")) {
            publicId = urn.substring(13);
        } else {
            return urn;
        }

        final boolean hasEscape = (publicId.indexOf('%') >= 0);
        if (hasEscape) {
            publicId = PublicId.stringReplace(publicId, "%2F", "/");
        }
        publicId = PublicId.stringReplace(publicId, ":", "//");
        if (hasEscape) {
            publicId = PublicId.stringReplace(publicId, "%3A", ":");
        }
        publicId = PublicId.stringReplace(publicId, ";", "::");
        publicId = PublicId.stringReplace(publicId, "+", " ");
        if (hasEscape) {
            publicId = PublicId.stringReplace(publicId, "%2B", "+");
            publicId = PublicId.stringReplace(publicId, "%23", "#");
            publicId = PublicId.stringReplace(publicId, "%3F", "?");
            publicId = PublicId.stringReplace(publicId, "%27", "'");
            publicId = PublicId.stringReplace(publicId, "%3B", ";");
            publicId = PublicId.stringReplace(publicId, "%25", "%");
        }

        return publicId;
    }

    /**
     * Replace one string with another.
     */
    private static String stringReplace(String str,
                                        String oldStr,
                                        String newStr) {
        int pos = str.indexOf(oldStr);
        if (pos >= 0) {
            final StringBuilder buffer = new StringBuilder();
            final int oldStrLength = oldStr.length();
            int start = 0;
            do {
                for (int i = start; i < pos; ++i) {
                    buffer.append(str.charAt(i));
                }
                buffer.append(newStr);
                start = pos + oldStrLength;
                pos = str.indexOf(oldStr, start);
            }
            while (pos >= 0);
            final int strLength = str.length();
            for (int i = start; i < strLength; ++i) {
                buffer.append(str.charAt(i));
            }
            return buffer.toString();
        }
        return str;
    }
}
